Since the processes are so affected by shear rates, obtaining information about the shear viscosity is the first step. Data acquisition via a direct capillary measurement is a good idea, although other techniques are acceptable. Linear properties and elongation data can also be used (either in the automatic fitting calculation or for checking the results of the automatic fitting), if they are available.

The extensional viscosity can be measured for moderate strain rates, usually up to 10 s^-1 using an elongational rheometer equipped with the Extensional Viscosity Fixture (EVF).